Light sensing method, physiological parameter computing method and light sensing system

ABSTRACT

A light sensing method, applied to a light sensing system comprising a light sensor and at least one light source. The light sensor comprises a plurality of light sensing units. The light sensing method comprises: controlling the light sensor to capture images according to the light source; generating an exposure condition according brightness that each of the light sensing units senses, to control all the light sensing units to generate a target brightness distribution according to the exposure condition; and controlling the light sensing units to sense light from the light source according to the exposure condition. The light sensing system can have a better SNR via adjusting the exposure condition for each one of the light sensing units. Such light sensing method can be applied to compute physiological parameters.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of applicant's earlier U.S. application,Ser. No. 15/672,312, filed 2017 Aug. 9, which claims the benefit of TWNapplication, Serial No. 106102771, filed 2017 Jan. 25. The contentsthereof are included herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a light sensing method, a physiologicalparameter computing method, and a light sensing system, and particularlyrelates to a light sensing method, a physiological parameter computingmethod, and a light sensing system which can increase a SNR (Signal toNoise Ratio).

2. Description of the Prior Art

In recent years, people pay more attention to their health. Accordingly,a wearable device which can measure a heart rate becomes more and morepopular. Conventionally, a heart rate measuring method uses a lightsource to emit light to a part of a human body, such as a finger or awrist, and then measures light reflected from the human body. By thisway, the heart rate can be acquired. The reason is: the blood amounts inthe artery are different during contraction of heart and duringrelaxation of heart, thus the absorbing levels for blood in the arteryare also different during contraction of heart and during relaxation ofheart. Accordingly, the heart rate can be acquired via measuring thereflection levels for the light.

However, the distances between light sources and light sensing units fora light sensor are different. Therefore, the same light source willcause different light response for different light sensing units in thesame light sensor. Thus, the SNR for light sensing signals is reduced,and the measuring for the heart rate is non-accurate.

SUMMARY OF THE INVENTION

Therefore, one objective of the present invention is to provide a lightsensing method and a light sensing system, which can cause a higher SNRwhile the light sensor sensing light.

Another objective of the present invention is to provide a more accuratephysiological parameter computing method.

Another embodiment of the present invention provides a light sensingmethod, applied to a light sensing system comprising a light sensor andat least one light source. The light sensor comprises a plurality oflight sensing units. The light sensing method comprises: controlling thelight sensor to capture images according to the light source; generatingan exposure condition according brightness that each of the lightsensing units senses, to control all the light sensing units to generatea target brightness distribution according to the exposure condition;and controlling the light sensing units to sense light from the lightsource according to the exposure condition.

Another embodiment of the present invention provides a physiologicalparameter computing method applied to a physiological parametercomputing system comprising a light sensing system including a pluralityof light sensing units and at least one light source. The physiologicalparameter computing comprises: controlling the light sensor to captureimages according to the light source; generating an exposure conditionaccording brightness that each of the light sensing units senses, tocontrol all the light sensing units to generate a target brightnessdistribution according to the exposure condition; and controlling thelight sensing units to sense light from the light source according tothe exposure condition.

Another embodiment of the present invention provides a light sensingsystem comprising: a plurality light sensing units; at least one lightsource; and a processing unit, configured to generate an exposurecondition according brightness that each of the light sensing unitssenses, to control all the light sensing units to generate a targetbrightness distribution according to the exposure condition; wherein thelight sensing units sense light from the light source according to theexposure condition.

In view of above-mentioned embodiments, the exposure conditions for eachof the light sensing units can be adjusted to cause the light source toprovide a proper light response to the light sensor. By this way, theSNR can be raised, and the accuracy for computing a physiologicalparameter can be increased as well. Additionally, the present inventionfurther provides a power saving mode to save power consumption.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a light sensing systemaccording to one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a more detail light sensingsystem according to one embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating how to control a lightsensing time for light sensing units, according to one embodiment of thepresent invention.

FIG. 4 is a schematic diagram illustrating that the light sensing systemoperates in a power saving mode.

FIG. 5 is a schematic diagram illustrating how to control a lightsensing time for light sensing units, according to one embodiment of thepresent invention.

FIG. 6 is a schematic diagram illustrating a light sensing systemaccording to another embodiment of the present invention.

DETAILED DESCRIPTION

In following descriptions, a plurality of embodiments are provided toexplain the concept of the present invention. Please note, eachapparatus, system, device or module illustrated in following embodimentscan be implemented by hardware (ex. circuit) or hardware with software(ex. program installed to a processing unit). Besides, the name, thenumber or the location for elements in each embodiment is only forexample and does not mean to limit the scope of the present invention.

FIG. 1 is a schematic diagram illustrating a light sensing systemaccording to one embodiment of the present invention. As illustrated inFIG. 1, the wearable apparatus 100 comprises a light sensing system 101,which comprises a light senor LS1, at least one light source (in thisembodiment, one light source L1, but not limited) and a processor 103.In one embodiment, the light senor LS1 is alight sensing diode matrix,and the light source can be a light emitting diode or a laser lightsource. In one embodiment, the light source can emit light having singlewavelength (ex. an infrared light source, or green light source) toincrease the sensing efficiency of the light sensor LSI.

The light sensor LSI comprises a plurality of light sensing units (ex. alight sensing diode or a group of light sensing diodes, not illustratedhere). The processing unit 103 respectively controls an exposurecondition for each of the light sensing units according distancesbetween each one of the light sensing units and the light source L1, andcontrols the light sensing units to sense the light from the lightsource according to the exposure condition. The exposure condition canbe: a light sensing time of a light sensing unit, a light sensingfrequency of a light sensing unit or a read signal gain value. The readsignal gain value means a gain value for light sensing signals read fromlight sensing units. Therefore, if a constant light response is desiredfor a light sensing unit far from the light source L1, a strongerexposure condition is needed. For example, increase the light sensingtime, the light sensing frequency, or the read signal gain value.

In one embodiment, the exposure condition is computed according to adistance between the light source and the light sensing unit, and thenthe exposure condition is stored to a register 105. The light sensor LS1reads the exposure condition from the register 105 before capture animage. In one embodiment, the register 105 can pre-store a predeterminedexposure condition, which can be decided by other factors rather than adistance between the light source and the light sensing unit. Afterthat, the exposure condition decided according to a distance between thelight source and the light sensing unit can be updated to replace thepredetermined exposure condition.

In one embodiment, the light sensing system 101 can operate in acalibrating mode. In the calibrating mode, the processing unit 103adjusts the exposure condition according to the sensed brightness, afterthe light sensor LSI captures an image according to light from the lightsource L1, thereby all the light sensing units can generate a targetbrightness distribution according to the adjusted exposure condition.The target brightness distribution can be any kinds of brightnessdistribution. For example, the target brightness distribution can be auniform brightness distribution, which means brightness difference forneighboring light sensing units or the difference between the maximumbrightness and the minimum brightness for all light sensing units islower than a threshold value. The new exposure condition is updated tothe register 105 after acquired.

FIG. 2 is a schematic diagram illustrating a more detail light sensingsystem according to one embodiment of the present invention. Asillustrated in FIG. 2, the light sensor LS1 comprises light sensingunits P1, P2. Please note other light sensing units are not illustratedor symbolized. The width for each of the sensing units is X, and thedistance between center points of the sensing units is also X. In oneembodiment, the X is 0.5 mm. For such structure, a difference between adistance from the light source L1 to the light sensing unit P1 and adistance from the light source L1 to the light sensing unit P2 is X,such that the light intensity which the light sensing unit P1 sensesfrom the light source L1 and the light intensity which the light sensingunit P2 senses from the light source L1 are different. Therefore, evenif the light sensing units P1, P2 have the same exposure conditions, thelight sensing units P1, P2 receive different light amount in the sametime period. Namely, the light source L1 causes different lightresponses to the light sensing units P1, P2. Accordingly, exposureconditions for the light sensing units P1, P2 must be different if thelight source L1 is expected to cause the same light response to thelight sensing units P1, P2.

FIG. 3 is a schematic diagram illustrating how to control a lightsensing time for light sensing units, according to one embodiment of thepresent invention. As illustrated in FIG. 3, in this embodiment, thelight sensing unit P1 is closer to the light source L1 and sensesstronger light, thus is set to have a higher light sensing frequency buta shorter light sensing time T1 for each time of exposure. Oppositely,the light sensing unit P2 is farer from the light source L1 and sensesweaker light, thus is set to have a lower light sensing frequency but along light sensing time T2 for each time of exposure. That is, a lightsensing frequency is inversely proportional to a distance between thelight sensing unit and the light source, and a light sensing time isproportional to a distance between the light sensing unit and the lightsource. Please note, in one embodiment, either the light sensingfrequency or the light sensing time is adjusted. In another embodiment,only one of the light sensing frequency and the light sensing time isadjusted. By this way, the exposure condition causes light amount thateach of the light sensing units P1, P2 receives from the first lightsource L1 in a predetermined time period is a predetermined lightamount. In other words, the light responses that the first light sourceL1 cause to the light sensing units P1, P2 are the same.

In above-mentioned embodiments, each of the light sensing units P1, P2receives from the first light source L1 in a predetermined time periodis a predetermined light amount, which means the light sensing systemoperates in a uniform mode. However, the light sensing system canoperate in a non-uniform mode as well. In another embodiment, theexposure condition causes light amounts that different light sensingunits receive from the first light source in a predetermined time periodare different. Namely, the exposure condition causes light amount thatthe light sensing unit P1 receives from the first light source L1 in apredetermined time period is a first predetermined light amount, andcause light amount that the second light sensing unit P2 receives fromthe first light source L1 in the predetermined time period is a secondpredetermined light amount. The first predetermined light amount and thesecond predetermined light amount are different. That is, the lightsource L1 causes predetermined but different light responses todifferent light sensing units.

The present invention also provides a power saving method, which cancontrol the light sensing system to operate in a power saving mode. FIG.4 is a schematic diagram illustrating that the light sensing systemoperates in a power saving mode. As illustrated in FIG. 4, the lightsource emits light for a plurality of times in a light emitting time LT,for example continuously emits light for a plurality of times, and doesnot emit light in a stop time ST consecutively following the lightemitting time LT, and then emits light for a plurality of times inanother light emitting time LT consecutively following the stop time ST.Lengths of the light emitting time LT, the stop time ST, and a numberfor emitting light can be set to any desired value. For a conventionallight emitting method, the light source continuous emits light, and isactivated for each time of light emitting. However, the light sourceenters a non-active state after emits light, and must be activated againfor the next time of light emitting. Therefore, the conventional lightemitting method consumes much power. Via the light emitting method inFIG. 4, the number for activating the light source can be decreased,thus the power consumption can be reduced.

In above-mentioned embodiments, a single light source is taken as anexample for explaining. However, the light sensing method provided bythe present invention can apply more than light sources. FIG. 5 is aschematic diagram illustrating how to control a light sensing time forlight sensing units, according to one embodiment of the presentinvention. As illustrated in FIG. 5, the light sensor LS1 compriseslight sensing units P1, P2, and the light sensing system comprises aplurality of light sources L1 and L2. In one embodiment, the lightsensing system operates in a uniform mode, which means exposurecondition causes light amount that each of the light sensing units P1,P2 receives from the first light source L1 in a predetermined timeperiod is a predetermined light amount, and causes each of the lightsensing units P1, P2 receives from the second light source L2 in thepredetermined time period is also the predetermined light amount. Thatis, the exposure conditions for the light sensing units P1, P2 cause thelight sources L1, L2 to generate the same light response to the lightsensing units P1, P2.

In another embodiment, the light sensing system operates in anon-uniform mode. In such embodiment, the exposure condition causeslight amount that each of the light sensing units receives from thefirst light source L1 in a predetermined time period is a firstpredetermined light amount, and cause light amount that each of thelight sensing units receives from the second light source L2 in thepredetermined time period is a second predetermined light amount. Thatis, the exposure conditions for the light sensing units P1, P2 cause thelight sources L1, L2 to generate different light responses to the lightsensing units P1, P2.

The light source can cause the same light response to different lightsensing units in the uniform mode, such that the SNR can be raised.Also, the light sensing system can have better SNRs for different statesin the non-uniform mode. Take the embodiment in FIG. 5 for example, thelight sensing system senses stronger environment light while in anoutdoor environment, thus the light source L1 is set to emit strongerlight and the exposure condition is adjusted following above-mentionedrules. By this way, the light source L1 causes a proper light responseto the light sensor LS1. In another example, the light sensing systemsenses weaker environment light while in an indoor environment, thus thelight source L2 is set to emit weaker light and the exposure conditionis adjusted following above-mentioned rules. By this way, the lightsource L2 causes a proper light response to the light sensor LS1.

In summary, the non-uniform mode causes the light sensing systemprovided by the present invention can operate smoothly in differentenvironments. Also, the non-uniform mode can make sure that at least onelight source causes proper light response to the light sensor, thus theapplication range for the light sensing system provided by the presentinvention can be extended.

In above-mentioned embodiments, a single light sensor is taken as anexample for explaining. However, the light sensing system provided bythe present invention can also comprise a plurality of light sensors anda plurality of light sources. FIG. 6 is a schematic diagram illustratinga light sensing system according to another embodiment of the presentinvention. Comparing with the embodiment in FIG. 1, the embodiment inFIG. 6 further comprises a light sensor LS2 and a light source L2. Inthis embodiment, different light sensors sense different light sourcesat different timings. For more detail, the operation that the lightsensor LS1 senses the light source L1, the operation that the lightsensor LS1 senses the light source L2, the operation that the lightsensor LS2 senses the light source L1, and the operation that the lightsensor LS2 senses the light source L2 are performed at differenttimings. By this way, the interferences between sensing operations canbe avoided.

In view of above-mentioned embodiments, a light sensing method can beacquired, which comprises following steps: A light sensing method,applied to a light sensing system comprising a first light sensor (ex.LS1 in FIG. 1) and at least one light source (ex. L1 in FIG. 1). Thefirst light sensor comprises a plurality of light sensing units (ex. P1,P2 in FIG. 2). The light sensing method comprises: (a) respectivelycontrolling an exposure condition for each of the light sensing unitsaccording distances between each one of the light sensing units and thelight source; and (b) controlling the light sensing units to sense thelight from the light source according to the exposure condition.

The above-mentioned light sensing method can be applied to measure aheart-rate, but also can be applied to measure other physiologicalparameters such as a degree of blood oxygen. Therefore, a physiologicalparameter computing method according to the above-mentioned lightsensing method can be acquired, which further comprises a following step(c) besides the above-mentioned steps (a) and (b). The step (c) is:computing a physiological parameter of a user according to light thatthe light sensing units senses in the step (b). If the apparatuscomprising the apparatus provided by the present invention (ex. thewearable apparatus 100 in FIG. 1) performs such physiological parametercomputing method, the apparatus can be regarded as a physiologicalparameter computing system. Besides, the step (c) can be performed bythe processing unit 103 illustrated in FIG. 1.

In view of above-mentioned embodiments, the exposure conditions for eachof the light sensing units can be adjusted to cause the light source toprovide a proper light response to the light sensor. By this way, theSNR can be raised, and the accuracy for computing a physiologicalparameter can be increased as well. Additionally, the present inventionfurther provides a power saving mode to save power consumption.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A light sensing method, applied to a lightsensing system comprising a light sensor and at least one light source,wherein the light sensor comprises a plurality of light sensing units,the light sensing method comprising: controlling the light sensor tocapture images according to the light source; adjusting an exposurecondition to an adjusted exposure condition for each of the lightsensing units, according brightness that each of the light sensing unitssenses, to control all the light sensing units to generate a targetbrightness distribution according to the adjusted exposure condition;and controlling the light sensing units to sense light from the lightsource according to the adjusted exposure conditions; wherein the stepof adjusting the exposure condition adjusts the exposure condition viaadjusting at least one of: a light sensing time of the light sensingunits, a light sensing frequency of the light sensing units and a gainvalue for light sensing signals read from the light sensing units.
 2. Aphysiological parameter computing method applied to a physiologicalparameter computing system comprising a light sensing system including aplurality of light sensing units and at least one light source, whereinthe physiological parameter computing method comprises: controlling thelight sensor to capture images according to the light source; adjustingan exposure condition to an adjusted exposure condition for each of thelight sensing units, according brightness that each of the light sensingunits senses, to control all the light sensing units to generate atarget brightness distribution according to the adjusted exposurecondition; and controlling the light sensing units to sense light fromthe light source according to the adjusted exposure conditions; whereinthe step of adjusting the exposure condition adjusts the exposurecondition via adjusting at least one of: a light sensing time of thelight sensing units, a light sensing frequency of the light sensingunits and a gain value for light sensing signals read from the lightsensing units.
 3. A light sensing system, comprising: a plurality lightsensing units; at least one light source; and a processing unit,configured to adjust an exposure condition to an adjusted exposurecondition for each of the light sensing units, according brightness thateach of the light sensing units senses, to control all the light sensingunits to generate a target brightness distribution according to theadjusted exposure condition; wherein the light sensing units sense lightfrom the light source according to the adjusted exposure conditions;wherein the processing unit adjusts the exposure condition via adjustingat least one of: a light sensing time of the light sensing units, alight sensing frequency of the light sensing units and a gain value forlight sensing signals read from the light sensing units.